1. Field of the Invention
The present invention relates to a dielectric recording medium and a dielectric recording/reproducing apparatus for recording information with high density in microdomains in a dielectric substance, especially in a ferroelectric substance, and reproducing information recorded in it.
2. Description of the Related Art
As conventional techniques associated with high-density information recording/reproducing, there are proposed optical recording, magnetic recording, thermal recording, ferroelectric recording and the like.
In the optical recording, an optical pickup with a laser as a light source is used. Data is recorded by forming pits that are concave-convex on a disk surface or forming the crystal phase of a phase shift medium. The recorded data is reproduced by using the difference in the reflectance of amorphous phases or using the magneto optical effect. However, the inertia of the pickup is relatively large, which is not appropriate for high-speed reading, and the size of the recording pit in using a focusing optical system, such as lens, is defined by the diffraction limit of light, so that its recording density is limited to 50 G bit/inch2.
In the longitudinal recording of the magnetic recording as represented by a hard disk drive (HDD), its recording density is limited to 100 G bit/inch2 due to thermal fluctuation. Moreover, a magnetic resistance (MR) head has been recently realized using giant magnetic resistance (GMR) and its recording density is expected to be larger than that of the optical disk by using perpendicular magnetic recording. However, the recording density is limited to 1 T bit/inch2 due to thermal fluctuation of magnetic recording information and the presence of a Bloch wall in a code reverse or sign change portion, even if patterned media are used considering the above cause.
As the thermal recording, there are a method in which polymer is used as a recording medium with a microheater formed at a probe tip, a method in which an electron emission source is used with a phase change material used as a recording medium, a method in which near-field light is used with the phase change material used as a recording medium, and the like. However, these methods have the limitations of the recording density, which is between 500 G and 1 T bit/inch2, due to intervening heat conduction.
Moreover, a recording/reproducing technique using a scanning nonlinear dielectric microscopy (SNDM) for the nanoscale analysis of a dielectric (ferroelectric) material has been also proposed by the inventors of the present invention.
However, with respect to dielectric recording/reproducing using the above-described SNDM, specific methods have not been presented for tracking control, address search control, and the like.